Subprocess timeout failure

Question

I want to use a timeout on a subprocess

 from subprocess32 import check_output
 output = check_output(\"sleep 30\", shell=True, timeout=1)

Answer 1

Update for Python 3.6.

This is still happening but I have tested a lot of combinations of check_output, communicate and run methods and now I have a clear knowledge about where is the bug and how to avoid it in a easy way on Python 3.5 and Python 3.6.

My conclusion: It happens when you mix the use shell=True and any PIPE on stdout, stderr or stdin parameters (used in Popen and run methods).

Be careful: check_output uses PIPE inside. If you look at the code inside on Python 3.6 it is basically a call to run with stdout=PIPE: https://github.com/python/cpython/blob/ae011e00189d9083dd84c357718264e24fe77314/Lib/subprocess.py#L335

So, to solve @innisfree problem on Python 3.5 or 3.6 just do this:

check_output(['sleep', '30'], timeout=1)

And for other cases, just avoid mixing shell=True and PIPE, keeping in mind that check_output uses PIPE.